In stereographic viewing systems of the type of the present invention, alternately displayed right and left stereographic images are viewed through a pair of viewing goggles or glasses wherein the lenses are shuttered to alternately open and close in synchrony with the images to produce a stereographic effect. Several different means are known for controlling the shutters and synchronizing their opening and closing to the display of the images, to assure that the right eye views the right eye images and the left eye views the left eye images, as required for a stereographic effect. U.S. Pat. No. 3,737,567 to Kratomi, issued Jun. 5, 1973, teaches the use of sound for this purpose. In U.S. Pat. No. 4,562,463 to Lipton, issued Dec. 31, 1985, an infrared signal is transmitted to infrared detectors in the viewing glasses. The signal is synchronized with the display of right and left images, and in turn controls the shuttered internal lenses in the viewing glasses. In Nakagawa et al., U.S. Pat. No. 4,772,943, issued Sep. 20, 1988, and Nakagawa et al., U.S. Pat. No. 4,870,486, issued Sep. 26, 1989, there is disclosed a shutter control system which, as best understood, is triggered by the refreshing of the CRT displaying the alternating right and left images.
One limitation in the Nakagawa system, and in other systems as well, is the ability to establish and maintain synchronization of the shutter control signal with the displayed images, as is essential to creating the stereographic effect. In particular, the Nakagawa system requires the user of the system to select the proper phase of the synchronization signal so that the right and left eye images are properly synchronized to the opening and the closing of the right and left shutters of the viewing glasses. Once synchronized, the system of Nakagawa will remain in synchrony so long as right and left eye images are alternately displayed. However, if a strict alternating display is not maintained, synchronization is lost. Thus, these types of systems cannot function where such alternating display cannot be guaranteed. One place where such alternating display cannot be guaranteed is in the field of computer generated graphics, where it is not always possible to guarantee the real time operation required for this purpose.
Other stereographic viewing systems suffer from the lack of portability from one system to the other. For instance, some systems require that the image information, or data, for each frame be coded with a header identification, as for example, those identifications used in a computer graphics application which specifies whether the image is a right eye image or a left eye image. This information can be identified by the computer system hardware, which in turn controls the shutters of the viewing glasses. Since there is not an industry standard system architecture/hardware for this purpose, the stereographic image files storing the alternating right and left images cannot be readily transported between different systems.
Thus, there is a need for a stereographic viewing system which is readily transportable from one system to another or one display medium to another, and wherein synchrony may be literally maintained irrespective of guaranteed alternation between right and left images.